Strings

A string file is the most common file format used to store information in Surpac. A string file contains coordinate information for one or more points, as well as optional descriptive information for each point. To enable you to work more efficiently with strings, it is important that you understand how Surpac organises and uses data stored within a string file.

String data hierarchy

Data in a string file is classified into:

• points
• segments
• strings

All points in a string file are grouped into segments, which are further grouped into strings.

The example below shows conceptually how a string file contains strings, which contain segments, which contain points.

Types of strings

There are three types of strings:

• open
• closed
• spot height

The table below explains these terms.

Surpac term	Common term	Example
Open string	Line	Drill hole trace
Closed string	Polygon	Property boundary
Spot height string	Points not associated with a line or polygon	Blast hole collar locations

Description fields

Points, strings, and segments can have one or more pieces of descriptive information associated with them. This information is stored in a description field. Description fields are named according to the order they appear. Description fields are named in the format D<incremental number>, such as D1, D2, D3.

For example, a closed segment representing an ore zone could have the gold grade, silver grade, and specific gravity stored in separate description fields.  If the information is stored in that order, they could be assigned as follows: 

D1:  gold grade

D2:  silver grade

D3:  specific gravity

Data numbering

Strings, segments, and points are identified by unique numbers. You can assign string numbers to represent particular features, such as string 1 for toes in a pit, string 2 for crests, and string 99 for spot heights. Surpac automatically assigns segment numbers and point numbers.

Data ranges

You can use a range to refer to groups of data numbers, such as strings, segments, and points.

The comma ( , ) is used for a range that includes a start, an end, and, optionally, an increment. You use the following format to specify such a range in Surpac:

<start>,<end>,<increment>

Note: When the increment is 1, you can use <start>,<end> without specifying the increment.

The semicolon ( ; ) is used to identify unique values, or to separate multiple ranges.

Here are some examples:

Data values	Range	Description
1 2 3 4 5 6 7 8	1,8	from 1 to 8, at an increment of 1 (implied)
1 3 5 7	1,7,2	from 1 to 7, at an increment of 2
2000 2200 2400	2000,2400,200	from 2000 to 2400, at an increment of 200
1 6	1;6	1 and 6
2 6 9	2;6;9	2 and 6 and 9
2 3 4 5 6 9	2,6;9	from 2 to 6 at an increment of 1 (implied) and 9
25 50 60 70 80 90	25;50,90,10	25 and from 50 to 90 at an increment of 10
3 6 9 12 15 20 30	3,15,3;20;30	from 3 to 15, at an increment of 3 and 20 and 30
5 10 15 20 40 50 60	5,20,5;40,60,10	from 5 to 20, at an increment of 5 and from 40 to 60, at an increment of 10

String file names

Surpac string file names have the following components:

Component	Description	Required?
Location	Any combination of characters and numbers	Required
ID	Numbers only	Optional
Extension	Always .str	Required

Here are some examples of file names:

File name	Location	ID	Extension
pit.str	pit		.str
bench105.str	bench	105	.str
2007design.str	2007design		.str
2007design2.str	2007design	2	.str
grade_control135.str	grade_control	135	.str
dhcomp2_50.str	dhcomp2_	50	.str
level-300.str	level	-300	.str

Spaces in file names are not recommended. In some situations, Surpac might not work correctly if you are using a file that has a space in the file name.

You can use ranges to refer to the ID of filenames. For example, you can refer to the files:

geo130.str, geo140.str, geo150.str, geo160.str, geo170.str

using the following syntax:

Location: geo ID: 130,170,10

String directions

When you view closed strings in the XY plane, the points have an order that is either clockwise or anticlockwise. This direction is important when calculating areas and volumes.

• Clockwise strings represent an area of inclusion.
• Anticlockwise strings represent an area of exclusion.

Viewing string data

Here is an example that demonstrates the previous concepts.

Task: View string data

1. Click Reset graphics .
2. Open bench105.str in Graphics.
3. Choose Display > Strings > With string and segment numbers.
4. Enter the information as shown, and click Apply.



The file bench105.str is displayed.



The data in this file represents a horizontal view, also known as a plan view, of a pit design, the survey stations, and the geology for one level in a pit. 

The data is organised as follows.

String number	Segment number	Data	Type	D1	D2	D3
1	1	Low grade ore	Closed	Gold (g/t)	Silver (g/t)	SG
2	1	Medium grade ore	Closed	Gold (g/t)	Silver (g/t)	SG
3	1	High grade ore	Closed	Gold (g/t)	Silver (g/t)	SG
8	1	Footwall trace	Open	footwall
8	2	Hangingwall trace	Open	hangingwall
30005	30005	Pit design toe	Closed
30008	30008	Survey stations	Spot height	Station name

5. Choose Display > Point > Numbers.
6. Enter a value of 1 for the String range, and click Apply.



The order of points for string 1 is clockwise in the XY plane.



7. Click Reset graphics .

Note: To see all the steps performed in this task, run 01a_viewing_string_data.tcl. You need to click Apply on any forms presented.

String file structure

Sometimes it is helpful to view the contents of a string file in a text editor.

Task: View string data in a text editor

1. From the Navigator, right-click bench105.str, and select Edit.

The file opens in your text editor.



• The first line is known as the header record, and contains these items: file name, date modified, purpose (which is empty in this example), styles file.
• The second line contains the axis record. This is a two-point line used in some sectioning functions. For many string files this is not required; when it is not required, values of zero are used for all coordinates. The Y, X, and Z values of each of the two end points of the axis are stored in the following order: Y(1), X(1), Z(1), Y(2), X(2), Z(2).
• The third line is the start of string data, and is stored as String number, Y, X, Z, D1, D2, D3, … D100.
• A null record indicates the end of a segment.
• String 1 is closed, because the first point and the last point are the same.
• When the file was created, the following values were chosen: D1 = gold (g/t), D2 = silver (g/t), and D3 = SG.  String 1 outlines an area of low grade ore with:
• a gold value of 1.23 grams/tonne.
• a silver value of 14.23 grams/tonne.
• a specific gravity of 2.7.
2. Scroll down in the file to see the data as shown.

• String 8 is open, since the first and last points are different.
• String 8 consists of two segments.
• String 30005 is closed, since the first and last points are the same.
• String 30008 is a spot height string with the survey station name in the D1 field.

3. Exit the text editor without saving any changes.

Note: Manually editing string files is not recommended. If the format becomes corrupt, Surpac may not work correctly when using the file.